Composite video with MSP430 chip

[NatureTM] used part of the Thanksgiving holiday to get composite video output working with an MSP430 microcontroller. He’s using one of the chips that came with the TI Launchpad, which is a big hardware limitation because of the relatively small code memory and RAM. The chip displays one still image at a resolution of 192×40 pixels. Still, this is a great way to learn about composite video signals, as a lot of other projects use a TVout library to save you the headaches. All you’ll need is a TI Launchpad, a 16 MHz crystal oscillator, two resistors, and an RCA jack. Dig through the code and see what a great job [NatureTM] did of offloading as much work onto the chip’s peripherals as possible.

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24 thoughts on “Composite video with MSP430 chip”

Wow, you got all that into a TI launch pad? No cheating? I’ve two of those just sitting here loosing value as we speak. No wonder they haven’t shipping my TI robot – they’re waiting to see if it’s worth the trouble. They didn’t ship it to you did they?

This made me finally open and assembly my launchpad, and i have no idea where to get started and get this onto the damn thing. I have all the software installed and the source loaded but after that i’m lost.

If its not colour, its not a composite video signal, since composite is the result from adding chroma and luma together. Its just a monochrome video signal.

While this is a nice hack and all that, I really do question the use of outputting an obsoleted video format on a microcontroller when it takes so much of its resources that you have virtually nothing left in it.

There is a void between these hacks and something like a beagleboard with a proper video out generator that is awaiting a product, but IMO analog SD video like these and the chumby make have no place these days other than curious.

Hey Richard, I thought of the fact that it’s not real composite, since it’s missing hue and saturation. I considered calling it “composite” with quotes every time, or “composite minus color.” I decided that the signal did contain brightness, sync, and blanking, so it was sort of a composite signal. It also does adhere to the NTSC composite standard. Think of it as a composite signal that’s only in B/W.

I used this “obsolete” video format because every TV, including very modern ones, have a composite input. It may be obsolete, but it’s still universal.

I think I was lucky. I ordered 2 direct from TI and got them. Someone at work ordered 2 as well. But he did so from DigiKey. He got those but had to pay shipping. If you really need one now you might try DigiKey. I am sure we and TI are working in a “far from consumer production supply chain” scenario and can expect a wide range of lead times.

@Richard

Hum, but the black and white signal does contain 1) vertical sync, 2) horizontal sync & 3) brightness. For many years that was all there was. Color came later and had to be added in such a way as to not disturb legacy equipment. I wasn’t around but assume, never the less, it did. As the color is a phase modulated signal added to everything else at about 3.8MHz, the black and white sets were probably sensitive to that signal as the brightness was able to be modulated all the way up to about 4MHz. So watching a color signal on an old black and white set probably added an annoying cheese grader pattern to everything. In the end, I’d still consider the output of this project to be composite video.

@NatureTM

If you wanted to add color, you might think about using s-video. I’m not sure exactly how it works, but Sony split the video (I’m going to call it) B&W composite from the color so as to preserve the higher bandwidth of the B&W composite signal. This plays right into how a VCR works and why Sony had such a better picture when used with VCRs. This way you don’t have to mix in yet another signal. Regardless I believe you sill have to add a color xtal (common as dirt I suspect) and some way to control the delay to simulate phase modulation (maybe just switching in and out extra gates?). Yes, you might be able to do it in software on a fast embedded processor. You would need to be able to move a 3.8MHz wave fractions of a wave cycle back and forth. So the processor would have to be moving several multiples of that. Say 64MHz, 128MHz or 256MHz depending on how many instructions you can get from one machine cycle.

@NatureTM, why not just say it puts out NTSC video? I think that’s what Parallax says about the Propeller (and they even do put out true composite with color, since the chip has special hardware to generate the color subcarrier).

@st2000 I have actually watched color TV broadcasts on a legacy TV that wasn’t designed for them (and built with vacuum tubes sometime around 1964), and there were no visible artifacts from the color signal. I don’t think those TV’s actually passed signals up to 4 MHz. In any case it was all very carefully designed to make sure those old sets worked OK, which is one reason the signal format is such an odd hack.

“I am sure we and TI are working in a “far from consumer production supply chain” scenario and can expect a wide range of lead times.” -st2000

I am in the same boat as VTL. From what I understand TI has made a name for themselves catering to smaller manufacturers. By screwing up the logistics of something like this says they don’t really cater to smaller markets. If your not going to do it right then they should have not bothered. For those that say that TI is not really to blame…. If McDonalds decided that they didn’t have the $$ to pay out the million dollar winner of their Monopoly game there would be Hell to pay. They got the benefit from the excitement generated from the game, then they should be able to pay out.

If you take a look around everyone is trying to gain a following. I think Microchip is currently taking 20% off of their kits (hint hint, I’d like a touch switch development board for Christmas). I think ST Micro is currently running a contest and might be selling their development board at a low price. And TI is just doing the same. Actually it is all a big win for us hackers who buy in small quantity.

On top of that, everyone has reduced their inventory. Face it, no one can afford millions of dollars of capital sitting around doing nothing these days. Even if you wanted 10,000 brand new processors, I think Microchip lead times are such that their more popular processors are not immediately available for the asking.

Just to follow up, I replied to the order confirmation saying that it was taking forever and the email bounced back. But the very next day I got a confirmation that it was shipped and I got the package today (3 month total wait).

If you want an MSP430 quickly you can just order the free samples, mine arrived in less than a week. Only downside is not having a board.